Naturally occurring vinca alkaloids, vincristine and vinblastine, at micromolar concentrations enhanced the ornithine decarboxylase activity in a dose-response manner in primary cultures of Ehrlich ascites carcinoma cells. After 8 h of culture in the presence or absence of vinblastine, cycloheximide was added to the medium, a 4.5-fold increase in the half-life of the ornithine decarboxylase act...

2-Difluoromethylornithine totally prevented any increases in putrescine and spermidine concentrations in the ventral prostate of castrated rats during a 6-day testosterone treatment. Prostatic ornithine decarboxylase activity was inhibited by 80%, whereas S-adenosylmethionine decarboxylase was stimulated by more than 9-fold. In seminal vesicle, the inhibition of putrescine and spermidine accumu...

A biphasic increase of putrescine concentration occurs in rat hepatoma tissue culture cells induced to proliferate. DL-alpha-Methyl ornithine, a competitive inhibitor of ornithine decarboxylase ( L-ornithine carboxylyase, EC 4.1.1.7) of hepatoma tissue culture cells, blocks the usual increases of putrescine and spermidine concentrations in these cells, and causes a rapid fall in the levels of p...

The activation of polyamine biosynthesis, dependent on increased gene expression of ornithine decarboxylase, has been found to play an important role in the control of cell proliferation and differentiation. In this report it has been found that accumulation of ornithine decarboxylase mRNA also follows stimulation of human monocytes/macrophages by tumor necrosis factor. Human recombinant tumor ...

The effect of various hormones on the activities of the four enzymes engaged with the biosynthesis of the polyamines has been investigated in the rat. Human choriogonadotropin induced a dramatic, yet transient, stimulation of l-ornithine decarboxylase (EC 4.1.1.17) activity in rat ovary, with no or only marginal changes in the activities of S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50), s...

1. The induction of ornithine decarboxylase activity in mouse 3T3 fibroblasts or an SV-40 transformed 3T3 cell line by serum was prevented by addition of the naturally occurring polyamines putrescine (butane-1,4-diamine) and spermidine. Much higher concentrations of these amines were required to fully suppress ornithine decarboxylase activity in the transformed SV-3T3 cells than in the 3T3 fibr...

Nerve growth factor (NGF) causes pheochromocytoma cells (PC12) to undergo a number of physiological changes which mimic the differentiated neuronal cell, including neurite extension. We have examined protein kinase C (Ca2+/phospholipid-dependent enzyme) as a potential signaling mechanism in NGF-stimulated neurite outgrowth and induction of the enzyme ornithine decarboxylase. Phorbol 12-myristat...

The activation of polyamine biosynthesis, dependent on increased gene expression of ornithine decarboxylase, has been found to play an impor tant role in the control of cell proliferation and differentiation. In this report it has been found that accumulation of ornithine decarboxylase mRNA also follows stimulation of human monocytes/macrophages by tumor necrosis factor. Human recombinant tumor...

Rats having a protein-free diet available ad libitum were fed a daily casein meal at the beginning of either the light- or the dark-phase of the day. A control group received a mixed-diet ad libitum. In all three groups, daily food ingestion was the same and casein corresponded to 12% of total intake. Liver activities of alanine, aspartate, ornithine and tyrosine aminotransferase, ornithine dec...